The present invention relates to an antitheft device for preventing the theft of a vehicle by disabling the ignition system of the vehicle.
There exists a wide variety of devices for preventing the theft of a vehicle, particularly by disabling the vehicle's ignition system. One vehicle antitheft device of this type is taught in Japanese Patent Publication No. 40577/1986. The device taught in this publication includes a mechanical steering lock mechanism which prevents the normal steering operation of the vehicle when the key has been pulled out from the ignition. The device operates by closing a switching element when the steering lock mechanism is destroyed or removed from the vehicle. A fuse is connected between a power supply and the ignition, with one end of the switching element grounded and the other end connected to a position between the fuse and the ignition means. The device prevents starting the engine when the steering lock mechanism has been destroyed or removed from the body of the vehicle by using the electric current from the power supply to blow out the fuse and thereby disable the ignition system.
However this antitheft device has several inherent drawbacks, the most notable being that it is possible to operate the ignition and start the engine of the vehicle by replacing the burnt out fuse with a new one, or by otherwise connecting the broken circuit using an appropriate conducting member. Since a vehicle may be equipped with extra fuses and such fuse replacement can be easily carried out by even those not skilled in the electrical art, this type of antitheft device does not always prevent an unauthorized person from starting the engine.
It is therefore an object of the present invention to provide an antitheft device which inhibits such reconnection of a broken circuit caused by destruction or removal of the steering lock mechanism and which may also aid recovery of a stolen vehicle equipped with this device.